Preparation and evaluation of monolithic capillary columns based on silica modified with polydimethylsiloxane (PDMS) for use in capillary liquid chromatography

Author(s)

Fabiane Pires

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2017-02-03

Examining board members

Carla Beatriz Grespan Bottoli; Álvaro José dos Santos Neto; José Alberto Fracassi da Silva

• Advisor: Carla Beatriz Grespan Bottoli

Abstract

The capillary monolithic columns have been evolving in the last years as a type of promising stationary phase in liquid chromatography (LC), following the miniaturization tendency in chromatographic systems and the continuous search for faster and more efficient separations. However, this type of stationary phase still have a lot to be improved to reach the efficiency of packed columns with sub-2 µm particles. Some of the main limitations are the shrinkages inherent of sol-gel process, the structure heterogeneity and the low reproducibility in prepare conditions. Due to this, this work aimed to optimize the prepare of this type of stationary phase with focus on sol-gel steps and capillary filling, in a first step. The technique employed to the application of the prepared stationary phases was the capillary liquid chromatography (CLC). Despite its many advantages, compared to HPLC, as the drastic reduction of solvent consuming, this technique is not so widespread yet, due to the necessity of a totally resized instrumentation to smaller volumes, and also, the limitation of commercial available stationary phases. This shows the increasing importance in development of new types of stationary phases to different applications. The aim of the second step of this work was the preparation of a new monolithic stationary phase based on polydimethylsiloxane (PDMS) immobilized onto silica to use in CLC. The preparation of stationary phases through polymer immobilization onto silica particles has already been extensively described before, but this process has never been made with monoliths. The methodology employed to prepare the monolithic supports was the performance of sol-gel process inside the capillaries; and to the preparation of the stationary phase was performed a self-immobilization step of the PDMS onto the monolith, followed by thermal immobilization and extraction. With all the optimizations steps, was possible to obtain a new stationary phase, with an efficiency of 79500 plates/m in the separation of 6 alkylbenzenes employing a mobile phase gradient (AU)

• FAPESP's process: 14/21866-9 - Preparation and evaluation of monolithic silica-based modified with poly (dimethyl siloxane) (PDMS) for use in capillary liquid chromatography
• Grantee: Fabiane Pires
• Support Opportunities: Scholarships in Brazil - Master